RADIUS - Packet Format
The packet format of Radius is as shown below:
Code: This is 1 Octet (1 byte) long and identifies various types of packets. Normally 1 Octet means 1 Byte.
Identifier: This is again 1 Octet long and aids in matching responses with requests.
Length: This is 2 Octets long and specifies the length of the packet including code, identifier, length, and authenticator. (Min packet is 20 Octets and max is 4096 Octets).
Authenticator: This is 16 Octets long and filled up in case of some requests and responses.
List of Attributes: There is a list of 63+ attributes and a Radius attribute will also have a defined format which is described in next chapter.